The 21-year-old Perez's reason for agreeing to the deal is simple -- he likes Kansas City.
"I play the game hard, work hard every day, and I want to be in Kansas City for, like, 20 years," Perez said.
By signing such a deal, Perez might sacrifice some higher salaries that could be achieved through the arbitration process or free agency.
"That's fine with me, because I want to play here," he said.
The ballclub, by guaranteeing a certain amount of money, takes the gamble that Perez will be worth it and will remain healthy.
"Every long-term deal always has a certain amount of risk," general manager Dayton Moore said. "Ultimately, will this player perform and produce over the lifetime of the contract? We believe Salvy will. Will he stay healthy? Well, he's 21 years old, as strong as a bull and works very, very hard."
Perez thanked the Glass family, which owns the Royals, Moore and many others who had a role in his signing and development.
"I like Kansas City. They gave me the chance when I was young," Perez said. "I want to play for Kansas City for a long time."
Perez had not yet shared his contract news with his mother, Yilda, who was at home in Venezuela.
"She doesn't know yet," he said, with a huge smile. "She may not sleep tonight."
Perez said he'd break the news gently so his mother doesn't get too excited.
"I'm going to take it slow, because she might die or something," he said with a deep laugh.
Perez didn't make his Major League debut until last Aug. 10, but he hit .331 and earned praise from pitchers for his game-calling in the 39 games he started at catcher.
Manager Ned Yost, a former catcher, remembers how impressed he was when he first watched Perez play.
"It took about two days for me to realize he was special," Yost said. "I've been in this game a long time. I've been at the big league level a long time and see hundreds of catchers come through. And I've never seen one like him. He's a very rare find."
Moore said that he and Yost had discussed the importance of signing Perez at the end of the 2011 season. He'd also heard from other players.
"Salvy talks to his teammates, and his teammates talk to us, and we're around each other every day," Moore said. "And Ned felt this was very important for us to do going forward. We talked about it the last game of the season -- that it'd be important to do something long-term. And some of our pitchers said, 'We need to keep this guy here long term.'"
Discussions with Perez's agent, Gustavo Vasquez, heated up about 2 1/2 weeks ago. The negotiations also involved Royals officials Dean Taylor, Jin Wong and Rene Francisco.
"It came together in the last 24 hours," Moore said, who added that the Royals pursued the deal aggressively. "We feel, to a man in this organization, that he exemplifies everything that we want in leadership and ability behind the plate at the catcher position."
Perez signed in 2006 at the age of 16.
"I started to dream about playing in the big leagues when I was 15 years old," he said. "When I was 15, some people in Venezuela told me I could sign and be in the big leagues. That's when I started thinking about it."
Now he has a long-term deal with Kansas City.
"He's the total package. I've never seen anybody that compares to him," Yost said.